ipa: raspberrypi: Pass the maximum allowable shutter speed into the AGC

In order to provide an optimal split between shutter speed and gain, the
AGC must know the maximum allowable shutter speed, as limited by the
maximum frame duration (either application provided or the default).

Add a new API function, SetMaxShutter, to the AgcAlgorithm class. The
IPA provides the maximum shutter speed for AGC calculations. This
applies to both the manual and auto AGC modes.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

4 files changed, 48 insertions, 15 deletions

diff --git a/src/ipa/raspberrypi/controller/agc_algorithm.hpp b/src/ipa/raspberrypi/controller/agc_algorithm.hpp
index 981f1de2..f97deb0f 100644
--- a/src/ipa/raspberrypi/controller/agc_algorithm.hpp
+++ b/src/ipa/raspberrypi/controller/agc_algorithm.hpp
@@ -19,6 +19,7 @@ public:
 	virtual void SetEv(double ev) = 0;
 	virtual void SetFlickerPeriod(double flicker_period) = 0;
 	virtual void SetFixedShutter(double fixed_shutter) = 0; // microseconds
+	virtual void SetMaxShutter(double max_shutter) = 0; // microseconds
 	virtual void SetFixedAnalogueGain(double fixed_analogue_gain) = 0;
 	virtual void SetMeteringMode(std::string const &metering_mode_name) = 0;
 	virtual void SetExposureMode(std::string const &exposure_mode_name) = 0;
diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp b/src/ipa/raspberrypi/controller/rpi/agc.cpp
index eddd1684..f4cd5d26 100644
--- a/src/ipa/raspberrypi/controller/rpi/agc.cpp
+++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp
@@ -157,7 +157,7 @@ Agc::Agc(Controller *controller)
 	  frame_count_(0), lock_count_(0),
 	  last_target_exposure_(0.0),
 	  ev_(1.0), flicker_period_(0.0),
-	  fixed_shutter_(0), fixed_analogue_gain_(0.0)
+	  max_shutter_(0), fixed_shutter_(0), fixed_analogue_gain_(0.0)
 {
 	memset(&awb_, 0, sizeof(awb_));
 	// Setting status_.total_exposure_value_ to zero initially tells us
@@ -227,11 +227,16 @@ void Agc::SetFlickerPeriod(double flicker_period)
 	flicker_period_ = flicker_period;
 }
 
+void Agc::SetMaxShutter(double max_shutter)
+{
+	max_shutter_ = max_shutter;
+}
+
 void Agc::SetFixedShutter(double fixed_shutter)
 {
 	fixed_shutter_ = fixed_shutter;
 	// Set this in case someone calls Pause() straight after.
-	status_.shutter_time = fixed_shutter;
+	status_.shutter_time = clipShutter(fixed_shutter_);
 }
 
 void Agc::SetFixedAnalogueGain(double fixed_analogue_gain)
@@ -261,7 +266,8 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode const &camera_mode,
 {
 	housekeepConfig();
 
-	if (fixed_shutter_ != 0.0 && fixed_analogue_gain_ != 0.0) {
+	double fixed_shutter = clipShutter(fixed_shutter_);
+	if (fixed_shutter != 0.0 && fixed_analogue_gain_ != 0.0) {
 		// We're going to reset the algorithm here with these fixed values.
 
 		fetchAwbStatus(metadata);
@@ -269,14 +275,14 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode const &camera_mode,
 		ASSERT(min_colour_gain != 0.0);
 
 		// This is the equivalent of computeTargetExposure and applyDigitalGain.
-		target_.total_exposure_no_dg = fixed_shutter_ * fixed_analogue_gain_;
+		target_.total_exposure_no_dg = fixed_shutter * fixed_analogue_gain_;
 		target_.total_exposure = target_.total_exposure_no_dg / min_colour_gain;
 
 		// Equivalent of filterExposure. This resets any "history".
 		filtered_ = target_;
 
 		// Equivalent of divideUpExposure.
-		filtered_.shutter = fixed_shutter_;
+		filtered_.shutter = fixed_shutter;
 		filtered_.analogue_gain = fixed_analogue_gain_;
 	} else if (status_.total_exposure_value) {
 		// On a mode switch, it's possible the exposure profile could change,
@@ -290,7 +296,7 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode const &camera_mode,
 		// for any that weren't set.
 
 		// Equivalent of divideUpExposure.
-		filtered_.shutter = fixed_shutter_ ? fixed_shutter_ : config_.default_exposure_time;
+		filtered_.shutter = fixed_shutter ? fixed_shutter : config_.default_exposure_time;
 		filtered_.analogue_gain = fixed_analogue_gain_ ? fixed_analogue_gain_ : config_.default_analogue_gain;
 	}
 
@@ -403,7 +409,7 @@ void Agc::housekeepConfig()
 {
 	// First fetch all the up-to-date settings, so no one else has to do it.
 	status_.ev = ev_;
-	status_.fixed_shutter = fixed_shutter_;
+	status_.fixed_shutter = clipShutter(fixed_shutter_);
 	status_.fixed_analogue_gain = fixed_analogue_gain_;
 	status_.flicker_period = flicker_period_;
 	LOG(RPiAgc, Debug) << "ev " << status_.ev << " fixed_shutter "
@@ -582,13 +588,15 @@ void Agc::computeTargetExposure(double gain)
 		target_.total_exposure = current_.total_exposure_no_dg * gain;
 		// The final target exposure is also limited to what the exposure
 		// mode allows.
+		double max_shutter = status_.fixed_shutter != 0.0
+				   ? status_.fixed_shutter
+				   : exposure_mode_->shutter.back();
+		max_shutter = clipShutter(max_shutter);
 		double max_total_exposure =
-			(status_.fixed_shutter != 0.0
-			 ? status_.fixed_shutter
-			 : exposure_mode_->shutter.back()) *
+			max_shutter *
 			(status_.fixed_analogue_gain != 0.0
-			 ? status_.fixed_analogue_gain
-			 : exposure_mode_->gain.back());
+				 ? status_.fixed_analogue_gain
+				 : exposure_mode_->gain.back());
 		target_.total_exposure = std::min(target_.total_exposure,
 						  max_total_exposure);
 	}
@@ -671,6 +679,7 @@ void Agc::divideUpExposure()
 	shutter_time = status_.fixed_shutter != 0.0
 			       ? status_.fixed_shutter
 			       : exposure_mode_->shutter[0];
+	shutter_time = clipShutter(shutter_time);
 	analogue_gain = status_.fixed_analogue_gain != 0.0
 				? status_.fixed_analogue_gain
 				: exposure_mode_->gain[0];
@@ -678,14 +687,15 @@ void Agc::divideUpExposure()
 		for (unsigned int stage = 1;
 		     stage < exposure_mode_->gain.size(); stage++) {
 			if (status_.fixed_shutter == 0.0) {
-				if (exposure_mode_->shutter[stage] *
-					    analogue_gain >=
+				double stage_shutter =
+					clipShutter(exposure_mode_->shutter[stage]);
+				if (stage_shutter * analogue_gain >=
 				    exposure_value) {
 					shutter_time =
 						exposure_value / analogue_gain;
 					break;
 				}
-				shutter_time = exposure_mode_->shutter[stage];
+				shutter_time = stage_shutter;
 			}
 			if (status_.fixed_analogue_gain == 0.0) {
 				if (exposure_mode_->gain[stage] *
@@ -740,6 +750,13 @@ void Agc::writeAndFinish(Metadata *image_metadata, bool desaturate)
 			   << " analogue gain " << filtered_.analogue_gain;
 }
 
+double Agc::clipShutter(double shutter)
+{
+	if (max_shutter_)
+		shutter = std::min(shutter, max_shutter_);
+	return shutter;
+}
+
 // Register algorithm with the system.
 static Algorithm *Create(Controller *controller)
 {
diff --git a/src/ipa/raspberrypi/controller/rpi/agc.hpp b/src/ipa/raspberrypi/controller/rpi/agc.hpp
index 05c334e4..0427fb59 100644
--- a/src/ipa/raspberrypi/controller/rpi/agc.hpp
+++ b/src/ipa/raspberrypi/controller/rpi/agc.hpp
@@ -78,6 +78,7 @@ public:
 	unsigned int GetConvergenceFrames() const override;
 	void SetEv(double ev) override;
 	void SetFlickerPeriod(double flicker_period) override;
+	void SetMaxShutter(double max_shutter) override; // microseconds
 	void SetFixedShutter(double fixed_shutter) override; // microseconds
 	void SetFixedAnalogueGain(double fixed_analogue_gain) override;
 	void SetMeteringMode(std::string const &metering_mode_name) override;
@@ -100,6 +101,7 @@ private:
 	void filterExposure(bool desaturate);
 	void divideUpExposure();
 	void writeAndFinish(Metadata *image_metadata, bool desaturate);
+	double clipShutter(double shutter);
 	AgcMeteringMode *metering_mode_;
 	AgcExposureMode *exposure_mode_;
 	AgcConstraintMode *constraint_mode_;
@@ -126,6 +128,7 @@ private:
 	std::string constraint_mode_name_;
 	double ev_;
 	double flicker_period_;
+	double max_shutter_;
 	double fixed_shutter_;
 	double fixed_analogue_gain_;
 };
diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
index 85aee6f7..ff14cfc4 100644
--- a/src/ipa/raspberrypi/raspberrypi.cpp
+++ b/src/ipa/raspberrypi/raspberrypi.cpp
@@ -1065,6 +1065,18 @@ void IPARPi::applyFrameDurations(double minFrameDuration, double maxFrameDuratio
 	libcameraMetadata_.set(controls::FrameDurations,
 			       { static_cast<int64_t>(minFrameDuration_),
 				 static_cast<int64_t>(maxFrameDuration_) });
+
+	/*
+	 * Calculate the maximum exposure time possible for the AGC to use.
+	 * GetVBlanking() will update maxShutter with the largest exposure
+	 * value possible.
+	 */
+	double maxShutter = std::numeric_limits<double>::max();
+	helper_->GetVBlanking(maxShutter, minFrameDuration_, maxFrameDuration_);
+
+	RPiController::AgcAlgorithm *agc = dynamic_cast<RPiController::AgcAlgorithm *>(
+		controller_.GetAlgorithm("agc"));
+	agc->SetMaxShutter(maxShutter);
 }
 
 void IPARPi::applyAGC(const struct AgcStatus *agcStatus, ControlList &ctrls)